1. Field of the Invention
The present invention relates to a valve and a micro fluid pump having the same, and, more particularly, to a valve including a discharge pipe filled with liquid such that the discharge pipe has a predetermined resistance pressure and allowing gas out of the capillary tube through the discharge pipe, when a gas pressure in the capillary tube exceeds the resistance pressure of the discharge pipe, and a micro fluid pump having the same.
2. Description of the Related Art
Recently, there has been actively developed a micro electro mechanical system (MEMS), which has been widely applied to various fields, such as genetic engineering, medical diagnosis, and new medicine development.
Especially, a lab-on-a-chip (LOC) technology has been proposed to perform all processes, including general chemical reaction and analysis, using a single chip in the micro electro mechanical system.
The LOC is used to integrate and automatically analyze sample pre-process, reaction, separation, and detection devices necessary for sample analysis on a small-sized chip, such as glass, plastic, or silicon, using a micro machining method.
The sample analysis using the LOC has an advantage in that experiments are possible only with the minimum amount of sample, and therefore, it is being widely used in a medical field, a chemical field, a diagnosis field, and a biological field in which it is difficult to obtain a large amount of sample.
In order to analyze a sample or a reagent using the LOC, however, a drive source for transferring the sample or the reagent by a micro unit is needed.
An example of a conventional drive source for driving the LOC is a micro pump. In this connection, a pump using a piezoelectric element, a pump using an electrical capillary phenomenon, a pump using gas generation and extinguishment due to electrolysis, and a rotary pump for introducing and discharging fluid using a rotor have been proposed.
FIG. 1 is a view illustrating the construction of a conventional micro pump, which is a pump for transferring fluid, such as liquid or gas, using interfacial tension changeable due to potential difference. The micro pump includes a gas chamber 120 having a predetermined volume, a capillary tube 110 having one end connected to the gas chamber 120, a transferring pipe 180 connected to the other end of the capillary tube 110 and having an introduction check valve 190 and a discharge check valve 200 mounted therein for allowing the fluid to be transferred only in one direction, a lump of mercury 130 disposed in the middle part of the capillary tube 110, the lump of mercury 130 having an electrical contact pin 150 mounted therein, an electrolytic solution 140 filled in the capillary tube 110 such that one end of the electrolytic solution 140 is adjacent to the lump of mercury 130 and the other end of the electrolytic solution 140 is adjacent to the fluid which is transferred, the electrolytic solution 140 having an electrode 160 disposed therein, and a power source 170 for applying voltage between the electrical contact pin 150 and the electrode 160.
The micro pump with the above-stated construction is operated as follows. When square-wave voltage or sine-wave voltage from the power source 170 is applied to the electrode 160, the interfacial tension of the lump of mercury 130 is changed by the applied voltage. When the interfacial tension of the lump of mercury 130 is periodically changed by the voltage, the lump of mercury 130 performs a reciprocating movement in the capillary tube 110 according to a cycle of voltage supply.
When the lump of mercury 130 moves toward the gas chamber 120 in the capillary tube 110, the electrolytic solution 140 and fluid positioned at the other end of the capillary tube 110, which is connected to the transfer pipe 180, also move toward the gas chamber 120. As a result, the introduction check valve 190 is opened so as to fill the vacant space, and therefore, external fluid is introduced into the other end of the capillary tube 110.
On the other hand, when the lump of mercury 130 moves away from the gas chamber 120 in the capillary tube 110, i.e., toward the transfer pipe 180, the electrolytic solution 140 also moves toward the transfer pipe 180. As a result, the pressure in the transfer pipe 180 increases, and therefore, the discharge check valve 200 is opened, whereby the fluid is transferred through the discharge check valve 200. These processes are repeatedly performed to continuously transfer the fluid.
However, more than a predetermined pressure must be formed in the capillary tube so as to operate the conventional micro pump, and, when the check valve malfunctions, the interior pressure of capillary tube is excessively increased.
Consequently, when medicinal substances are injected into a human body using the conventional micro pump, the human body may encounter a dangerous situation.
Furthermore, the conventional micro pump is constructed in a structure in which the lump of mercury moves due to the application of external voltage so as to introduce or discharge the fluid. Consequently, it is necessary to include not only the gas but also the lump of mercury and the electrolytic solution in the capillary tube and dispose the electrical contact pin in the lump of mercury, which complicates the structure of the micro pump.